Attribution of the unprecedented heat event of August 2023 in Barcelona (Spain) to observed and projected global warming

Resumen

The study analyses observed and numerical simulations of daily maximum and minimum temperature from 1920 onwards and to investigate the unprecedented heat event that occurred in 21–23 August 2023 in Barcelona. The historical changes in the intensity of such events, their expected future changes under scenarios of +1.5 °C, +2 °C, and + 3 °C, and the future exposure of populations to such kind of events are examined using the flow analogues approach. The findings indicate a significant increase in observed temperatures for similar heatwaves to those occurred in August 2023. The study also emphasises the impact of global warming on the intensification of heat events over the impact of urbanization. Additionally, after examining the role of natural variability in temperature changes, we concluded that global warming is the primary factor driving the increase in heatwave intensity. In terms of the frequency of such events, we found that extreme heat events, such as the August 2023 heatwave, will become 2 and 5 times more likely with a global summer warming of 2 °C and 3 °C, respectively. This will expose a large portion of the population to dangerous heat levels highlighting the importance of limiting global warming to 1.5 °C to mitigate the impacts on urban populations.